JVM runtime data area

Runtime data is living in execution of application.
Some of data area are JVM-wise, means they create upon JVM startup and destroy when JVM shutdown.
Other data are thread specific, means their lifecycle is binded with thread lifecyclej

PC register(thread)

Each JVM thread has its own pc.

1. The value will be the address of JVM instruction + return address of currently thread
2. undefined if the current method is native

JVM stack(thread)

Each thread has its own stack.
Similar to the stack in C.
Does not have to be contiguous.

1. StackOverflowError if wants to have larger stack than permitted, larger in turns of the number frame
2. OutOfMemoryError if wants to have more memory space than permitted

Heap

Heap is shared amongst all JVM threads.
Heap storage is managed by GC.
Heap can be fixed, expandable and shrinkable.
The memory does not need to be contiguous.

1. OutOfMemoryError if wants to have more memory space than permitted

Method area

Shared amongst all JVM threads
It is the text segement in ASM.
Can be fixed, expandable and shrinkable.
The memory does not need to be contiguous.
This area does not have to GC

• OutOfMemoryError if wants to have more memory space than permitted

Contains class structure:

1. runtime constant pool
2. field data
3. method data
4. method code & constructor
5. static block/method

native method stack(thread)

A C stack will be created for all native method
Allocated per thread.
Can be fixed, expandable and shrinkable.

1. StackOverflowError if wants to have larger stack than permitted, larger in turns of the number frame
2. OutOfMemoryError if wants to have more memory space than permitted